Method of making a hard and compact metal for use in formation of tools, dies, etc.



Oct. 18, 1938. F. H. WILLEY 2,133,495

METHOD OF MAKING A HARD AND COMPACT METAL FOR USE IN FORMATION OF TOOLS.DIES, ETC

Filed Feb. 15, 1937 2 Sheets-Sheet l INVENTOR. 1 9/ M/As y HI I I LWHHII I l I I I I I I I. I

HMWWHH I I I 'HHHHHWW ATTORNEY.

Oct. 18, 1938. F. H. WILLEY 2,133,495 METHOD OF-MAKING A HARD ANDCOMPACT METAL FOR USE IN FORMATION OF TOOLS. DIES, ETC

Filed Feb 15 1937 2 Sheets-Sheet 2 INVENTOR. Fay M ///e y 5M 27%ATTORNEY.

III'IIL II. .IIII IIII Patented Oct. 18, 1938 UNITED STATES PATENTOFFICE METHOD OF MAKING A HARD AND COM- PACT METAL FOR- USE IN FORMATIONOF TOOLS, DIES, ETC.

10 Claims.

This invention relates to the method of forming hard, compact metalbodies suitable for tools such as cutting, drilling and surfacing tools,drawing dies, molds and other implements required to be formed of a hardmetal and commonly formed of a composition of metals such as any of themetals of the 6th group of Mendelejefi-s Periodic Table together with ametal of the iron group, carbon and additive elements such 10 asmolybdenum, chromium, boron, silicon, antimony etc.

This application is a continuation in part of my application Serial No.24,068, filed May 29, 1935, which has issued as Patent 2,074,038, dated5 March 16, 1937, the invention herein disclosed not being confined inspecific quantities or characters of the materials utilized which mayvary considerably due to the character of the tool to be produced ashereinafter described.

Heretofore, in this general art, it has been proposed to make a metalbody of a number of elements by powdering the same and submitting thepowder to pressure and sometimes heat to form a solid body and thensubmitting the same to-a sintering temperature in a furnace, thesintering temperature being from around 1100 to 1350 degrees 0.,depending somewhat upon the composition.

Examples of this type of tool and method of makingthe same are disclosedin the U. S. patents to Schroter, Nos. 1,551,333 and 1,727,909, Gilson,No. 1,756,857 and others. In'all of these cases the bodies are submittedto a sinte'ring temperature as a final treatment and are what isordinarily termed solid bodies that, nevertheless, have voids more orless and therefore do not provide the desired density and also are moreor less but not uniformly granular and therefore to some degree unfittedfor formation of the highest type of element such as a die, abrading, orcutting tool, element of wear resistant character as the sinteredmaterial will not take a uniformly high polish by a grinding operationand therefore does not provide the best structural characteristicssuiting the same for use as bushings or centers for lathes and variousother places where a hard and dense tool or element is required.

It is pointed out that this invention is not confined to the specificquantities of the materials utilized but rather to the method wherebythe elements may be formed into a tool of the greatest compactness andto a commercial degree free from a granular condition. An object of theinvention further is to reduce in electric welding machines.

the time required in the formation of the tool in comparison with thesintering method, as heretofore performed.

By my improved method as is hereinafter more fully described, I am ableto make a tool from the 5 powdered materials to a final formation of thesame in a period of less than five minutes and the tool produced by themethod is superior to the tools formed by the sintering methods nowcommonly in use and suggested by the above men- 10 tioned Letters Patentof the United States. Thus the invention exists in the method offormation of the metal body rather than in any specific compositionutilized.

These objects and features of the invention are l5 attained by means ofa press which may be of any approved form in which the entire treatmentof the material takes place and in the use of which gases are eliminatedfrom the material and thus voids prevented and due to the tempera- 20tures and pressure employed in the final stages,

a very hard dense body is produced which may thereafter be finallyshaped in the formation of the desired character of implement or device.

These and other objects and features of the in- 25 vention arehereinafter more fully described and claimed, and a machine by which theprocess may be readily performed is shown in the accompanying drawingsin which- Fig. 1 is a side elevation partly in section of 30 aconvenient form of press utilized in the formation of the implement.

Fig. 2 is a planview of the bed of the machine taken on line 2--2 ofFig. 1.

Fig.3 is an elevation of the upper part of the 35 machine taken from theright side of Fig. 1.

Fig. 4 shows a mold with an article therein in the process of beingformed.

The mechanism shown for producing the article is an electric weldingmachine which, as 40 shown in Fig. 1, has the water. cooled electrodes land 2. A crucible is shown at 3 as being positioned therebetween andresting upon a water cooled base 4. These electrodes are apertured asshown to permit water to flow through the body 45 thereof, the watersupply conduits therefor not being here shown, nor are the electriccircuits for the electrodes shown as such element is usual The electrode2 is supported in a carrier 5 which is movable on the 50 base 6 of themachine by means of a hand wheel 7, the electrode 2 being retracted topermit introducticn of the crucible and then moved forward by means ofthe screw until the crucible is held in pressure contact between theelectrodes. The 55 crucible lined with carbon or graphite. In eithercase, the graphite element is recessed as indicated 'at 8 in Fig. 4 andis preferably slightly coned at 5 the bottom 9. A verticallyreciprocable plunger III has a molybdenum or other hard metal tip forentering the recess and is supported by the holder H reciprocable in thebracket I2 attached to the standard l3'which in turn is supported on thebase 6. The bracket l2 supports the holder from lateral displacement andsustains it in truly vertical position.

The upper end of the standard l3 has a cham-, bered head l4 securedthereto within which is a coiled spring Hi. The upper end of thechambered member is threaded 'to receive a plug l8 having a centralprojection l'l engaging in the end coil of the spring and centering thesame and this may be adjusted to increase or decrease the normal tensionon the spring.

At the bottom of the chambered member M is a spring seat I8 having aprojection entering the bottom coil of the spring to center the same andthe member I8 is centrally threaded to re- 5 ceive a threaded-sleeve l9which is adjustable longitudinally in the spring seat l8. A stub shaft28 extends through the sleeve and is secured in place by the nut 2!. Thelower end thereof is in the form of a yoke 22 which receives a plate 3023 pivoted thereto by a pin 24. The opposite end of the plate is formedwith a yoke'25 in which an end of the link 26 is pivoted, the oppositeend being pivoted to the upper end of the holder II by the pin 21. Tothe plate is secured a han- 5 dle 28. The link and plate form a togglebetween the yoke at the upper end and. the holder II at the lower endand by operation of the handle,

the holder and the plunger member or tamp I0 may be reciprocated. Thenormal position of the 40 parts is indicated by dotted lines in Fig. 1and rwhen pressure is applied to the material in the crucible or mold,the handle 28 is moved downwardly as indicated byfull lines in Fig. 1.

In order that pressures to be applied may be 45 determined, the screwseat I8 is provided with a finger 29 extending through a slot 30 in thechambered member I4 and a calibrated gauge plate 3| is secured to themember l4 across which the finger is movable enabling the operator todetermine the pressure applied by downward movement of the handle 28.'The pivot pins 20 and 21 extend to one side of the leverage mechanismas shown in Fig. 3, and a coiled spring 32 is attached thereto tendingnormally to hold the 55, handle up with the plunger l8 out of the recessof the crucible as shown in dotted lines in Fig. 1.

One of the purposes of use of the Welding machine or likeinstrumentalityis to enable the article to be completely formed therein. It has 60heretofore been the practice to compact a material and even to heat itsomewhat in a machine of this character and then remove the mold orcrucible and complete the temperature treatment in a furnace or toremove the material after 65 heating sufiiciently to retain its shapeand subjecting it to a sintering temperature in a furnace. However, inthe method hereinafter described and in order to secure a tool of theproper'hardne'ss and density, the entire treatment of the material iscompleted in the welding machine thus not only saving the .labor cost ofhandling but also saving considerable equipment and permitting the toolto be completed under ahigh pressure while it is at a temperature abovethe sintering tem- 75 perature and it also enables the entire processcrucible may be carbon or graphite or a metal to be performed while thematerial is prevented from oxidation as it is protected from atmosphereduring the forming operation and also by being encased in a graphitecrucible and at the temperature attained creates a reducing atmosphere.

This in turn unites with the oxygen present to form carbon monoxidewhich is driven-01f as a gas by the pressure obtained thereby removingthe oxide from the material.

As an instance and not by Way of limitation, I form a powder containingapproximately 60 to 70 per cent tungsten (W) and 3 to 5 per cent carbon(C) and the balance nickel (Ni) and ball mill the same for a number ofhours suflicient to produce avery fine powder. Usually the material isplaced in the mill in more or less of a granular form and ball milledfor upwards of 400 hours, dependent more particularly upon the characterof the material, it being desirable to produce a powder of greatfineness such for instance as will pass a 350 mesh screen or finer. Informing a hard metal body of any suitable specific composition, a smallquantity of the powder is placed in a graphite mold and pressed ortamped by the plunger I0 of the press through operation ofthe handle 28,the pressure being insuflicient to raise the spring seat IS. A secondquantity is then placed in the crucible and tamped and this is repeateduntil the desired depth in the mold is secured. This depth, as may bepreviously determined by experience, is such that the tool, whencompleted, will be of the proper length and somewhat less than thelength of the tamped material. A graphite button of a size to slidablyfit in the mold, as indicated in Fig. 4, is placed on the top of thematerial and pressure applied thereto and at the same time electriccurrent is applied to the electrodes.

The pressure is comparatively light in this first step and thetemperature is sufiicient to bring the material to about 800 degrees C.for a short period and then current is cut off and the pressure releasedusually by withdrawal of the plunger to more readily permit the gases toescape from the mold. During this interval the material cools quiterapidly due to'the water cooling the electrodes in contact with the moldor crucible. Then a higher degree of pressure is applied and currentsupplied to the electrodes and the material is then held under pressureuntil a higher temperature is secured which may be determined in theusual manner. This heating under pressure and cooling proceeds throughthree or four successive stages of about one minute each in the makingof a tool or tip of approximately an inch in length and a diameter ofabout fifteen-sixteenths of an inch. With the specific composition abovemen tioned, the last stage should be at the temperature of the order of1700 degrees C., and a pressure of about 10,000 pounds per square inch.This will produce a plastic, or not quite molten, condition of themetaland, as gases have been constantly driven off from the material orabsorbed in the previous stages of heating and cooling, this. finalstage is performed with practically no gas present in the body underpressure and the metals practically alloy at approximately thetemperature stated and produce a body that is free of voids and ofgranular appearance, and of great hardness and density. By thesuccessive stages of increasing temperature and pressure and time periodtherebetween, opportunity is provided permitting completion of thereaction between the tungsten powder (W) and the free carbon '(C). Ifthe powdered material be brought to final high pressure and temperatureabout four stages of increasing heat and pressure in a single step, theresultant alloy will be of a coarse grained crystalline form and onpolishing will show free carbon.

In the sintering process heretofore in use, the metal has not been veryhighly heated prior to being placed in a furnace and raised to sinteringtemperature. In thus raising the temperature from about 800 degrees C.to approximately 1350 degrees C. which is the sintering temperature ofthe composition, considerable gas is produced which tends to cause thevoids heretofore mentioned. My improved process distinguishes in thatthe heating is very rapid and not slow as in the. furnace at'sinteringtemperature and is maintained under high pressure at a temperature abovesintering so that the material approaches a molten condition and a moreperfect alloy is secured as well as much greater density. 7

The above materials in the operation take up carbon from the crucibleand tend to form a highly carburized surface of the treated metal andthe tungsten, nickel and carbon combine to form a very hard and toughstructure not brittle in character and therefore free from cracking orshatter of the tool in use. The same materials at sintering temperaturein the metals heretofore utilized are naturally more brittle andalso dueto the voids present therein, provide a tool that will readily breakunder shock or impact all of which is avoided by my improved process.

The above description of procedure with the tungsten, nickel and carbonis only given by way of example. With a different percentage of nickelfor instance, or different materials as has heretofore been indicated,the final temperature may vary somewhat due to differences in meltingpoint temperature etc., the essential characteristics of the processbeing that preferably the metals are only brought to a condition justshort of the molten condition as heretofore stated. Principally becauseif a molten condition or liquefaction of the metal exists it isdifficult to hold it under the pressures to which the material issubmitted at the high temperature. It is pointed out, however, that witha proper character of mold and proper character of fitting of theplunger III or the button 33 the material could be brought to a moltencondition without material loss of metal. The invention therefore is notrestricted to the exact temperatures above set forth because it ispossible to carry the temperatures higher even with the specificcomposition set forth and also the temperatures may be lower than isstated with the specific composition due to the melting point of thecomposition being lower. It is preferable to submit the material to inbringing the material to the final temperature and pressure and removalof the plunger from the mold at each step to permit escape of the gasesas it is essential that the gases should be practically excluded orabsorbed prior to the final heating and pressure. a

It is also evident that variation in the composition is within the scopeof the invention because some implements or articles require to be lesshard than others and to have other qualities or characteristics thanhardness or wear resistance as will be readily understood by thosefamiliar with present day tools of the tungsten carbide type-that is,the tungsten may be replaced with some other element or used in lessquantity and other elements included such as titanium or other metal ofthe 6th group of Mendelejefis Periodic Table. The principal otherelement is a metal of the iron group-that is,

iron, cobalt or nickel as may best serve the purpose in securingpractically an alloy of materials and avoid granular condition.

In all the experiments that I have performed withdifferent metals of thegroups stated or different percentages of metals, the final temperaturehas not exceeded 1850 degrees C. and may be as low as approximately 1500degrees C. and pref;- erably at least slightly above a sinteringtemperature for the composition.

A major feature of the invention resides in the use of a high pressureat approximately the alloying temperatures of the metals utilized. It isalso preferable that in case of use of any of the metals of the 6thgroup of Mendelejeffs Table, it is. desirable that its avidity forcarbon should be unsatisfied but not wholly so as the metal having theavidity for carbon will, during the process, absorb some carbon from thecrucible or mold.

While I have shown a machine having only a single plunger and thereforecapable of making but one element at a time, it is obvious that themachine may have several plungers and arranged to apply current to acorresponding number of crucibles whereby a number of metal elements maybe made in the same time period.

It is further to be realized that the time period may be varied but inthe specific compositions hereinbefore mentioned, of tungsten, nickeland carbon, the succeeding steps of increasing temperature andpressuresmay each be performed within a time period of even less thanone minute in about four steps including the first and final heatingstep but the steps may be increased in number if desired or as may berequired with some compositions and the period of time may be variedwithout departing from the spirit and scope of the invention as setforth in the appended claims.

From the foregoing description, it is believed evident that the variousobjects and features of the invention are attained by the method offormation of the hard metal article as hereinbefore described, and thatthe major features of the invention reside in the formation of an alloyof metals'such as hereinbefore stated while the material is protectedfrom atmosphere to prevent an oxidation thereof and that the entireseries of steps except the ball milling of the material to form thepowder maybe performed in 2. single purpose machine and with greatrapidity and provide an article of greater density and hardness than hasheretofore been secured by the previously known sintering method.

Having thus fully described my improved process for forming variousarticles to secure a hard and compact metallic body, what I claim anddesire to secure by Letters Patent of the United States is- 1. Themethod of making a hard, dense metal body for the formation of variousdevices such as described, which consists in reducing to finely powderedform a metal of the 6th group of Mendelejeffs Table in major quantity,"a metal of the iron group in minor quantity, the presence of whichreduces the melting point temperature of the alloy, a quantity of carbonless than that required to satisfy the avidity 0f the metal of the firstgroup therefor, a small quantity of metal carbon button on the top ofthe material in the mold for engagement with the plunger, and submittingthe material to heat as by means of an electric current and to pressureby means of the plunger in a series of steps of first a comparativelylow temperature and pressure to start degasification of the materials,removing the plunger to permit an escape of the gases and then, througha succeeding series of more than two steps of increased pressure andheating and elimination of gases until a final step of high pressure andtemperature at which the materials will allo is attained.

2. The method of forming a hard and dense metal body for the making oftools, dies and the like which consists in the forming of a very finepowder of the following composition namely, a metal of the 6th group ofMendelejefis Table in major quantity, a minor quantity of metal of theiron group, and a percentage of carbon, then filling a mold with thepowdered material positioned therein in small quantities and tamped asthe mold is filled, then subjecting the mass to a light pressure andheating the material to a temperature of approximately 800 degrees C.,then, by succeeding steps of increased temperature and pressure andelimination of the gases therebetween, raising the same to a temperaturein the neighborhood of 1700 degrees C. while under a pressure ofapproximately 10,000 pounds per square inch, allowing the same to coolbetween the succeeding steps, and finally removing the same from themold.

3. The method of forming a hard and compact metal body for the formationof various implements such as described, which consists in reducing acomposition containing the desired metals and carbon to a very finepowder, placing the same in a mold and then subjecting the same to a lowpressure and heat to start degasification of the material, permittingthe gases to escape from the body, and then, in a series of succeedingsteps of increasing pressure and temperature and an intervening periodof reduced pressure and tem perature permitting discharge of the gasestherebetween, finally submitting the same to a pressure of approximately10,000 pounds per square inch and to a temperature at which the metalswill alloy, and then, when cooled, removing the same from the mold.

4. The method of making a hard compact metal body which consists infirst reducing to finely powdered form a metal of the 6th group ofMendelejeifs Periodic Table in major quantity, a metal of the iron groupin minor quantity, and carbon insufiicient in quantity to satisfy theavidity of the metal of the first mentioned group therefor, subjectingthe powdered material to pressure and heat in a form in a series ofsuccessive steps of increasing pressure and temperature and relievingthe material of pressure and temperature between the steps to permit anescape of gases, and as a final step, submitting the material to a highpressure and a temperature-productive of a plastic condition of thematerials practically free from gases within the body thereof whereby adense and hardmetal body is formed.

5. The vmethod of producing a hard compact metal body free from voidsand granular condiperiod therebetween for elimination of generated gasesbetween the steps until a final pressure of approximately 10,000 poundspersquare inch anda temperature at which the materials become plastic isattained.

6. The method of forming a hard compact metal body for the production ofvarious imple'- ments such as described which consists in first forminga fine powder of a number of elements together productive of therequired physical characteristics and then forming an alloy of themetals by submitting the powder while in a mold and shielded fromatmosphere to a series of successive steps of increasing pressure andtemperature and cooling between the steps until a plastic condition ofthe materials is produced while under a pressure of approximately 10,000pounds per square inch.

7. The method of making a hard and compact metal body which consists insubmitting a finely powdered'mass of metals while in a mold to a seriesof steps in which the metal is heated under successively increasingpressure and temperature and an intervening time period wherein themetal is cooled and freed of formed gases, until a final pressure ofapproximately 10,000 pounds per square inch is attained as the metalsare at alloying temperature.

8. The method of forming a hard and compact metal body which consists insubmitting a series of metal elements together productive of the desiredhardness and while in a mold and in a finely powdered form to a rapidlysucceeding series of steps of increasing heat and pressure, and coolingthe material between the said steps until the material finally attains aplastic condition while under high pressure.

9. In a method of forming a hard and compact metal body for the purposeof making implements requiring such characteristics, the step whichconsists in submitting the material while in a mold to pressure and heatin successive stages of increasing pressure and temperature andintervening periods of reduced pressure and temperature until thematerial finally attains a plastic condition while under high pressure.

10. The method of producing a hard and compact metal body which consistsin subjecting a powdered metal mass, while in a mold and shielded fromatmosphere and within a period of approximately five minutes of time, toa series of rapidly succeeding steps of simultaneously increasingtemperatureand pressure, and intervening periods of reduced pressure andtemperature wherein the material is freed of generated gases, until adesired high'pressure is attained as the materials attain alloyingtemperature.

FAY H. WILLEY.

